/Engine/Plugins/Animation/RigLogic/Source/RigLogicLib/Public/status/Status.h
The value will be 0 when the hook is invoked for the status message itself, and from 1..N for any of the arguments used for interpolating the status message. Although the hook is invoked only for const char* arguments, the indices will still denote their actual position in the argument list.
typedef const char *(*)([StatusCode](API\Plugins\RigLogicLib\status\StatusCode), std::size_t, const char *) HookFunction